Dimming circuit and apparatus for gaseous discharge lamps



ug- 17, 1965 c. E. STRECKER 3,201,645

DIMMING CIRCUIT AND APPARATUS FOR GASEOUS DISCHARGE LAMPS Filed Sept. 2, 1959 2 Sheets-Sheet 1 Aug. 17, 1965 DIMMING CIRCUIT AND APPARATUS FOR GASEOUS DISCHARGE LAMPS Filed Sept. 2 1959 c. E. STRECKi-:R 3,201,645

2 Sheets-Sheet 2 United States Patent Office .ii-,dllih Patented Aug. l?, i965 32H5/i5 Blain/ENG CIR-GUET ANB APEARA'EUS FR GASEUS DESYCHARGE LAMPS Charles E. Sneeker, deceased, iate of Danville, lli., by .leanne E. Strecken', executrirr, Marietta, Ghia, assigner General Eiectric Company, a corporation of New ork Filed Sept. 2, 1959, Ser. No. 333,619 l2 Elaims. (Ci. 315-98) This invention relates to electrical circuits and apparatus for regulating the luminous intensity of gaseous discharge lamps and more particularly to a dimming circuit and apparatus for operating one or more fluorescent lamps from an alternating current source at various levels of luminous intensity.

The invention is applicable to discharge lamps having activated filamentary cathodes which are continuously heated clurinor the operation of the lamp by a constant supply of current. ln the industry lamps of this kind are commonly known as rapid start or hot cathode lamps. A principal characteristic of rapid start lamps is that the cathodes can be brought to thermionic emission at voltages below the ionization voltage of the gas or vapor in the lamp since the cathodes are continuously heated while the lamp is in operation.

In the past various difficulties have been experienced in the operation of apparatus for dimming uorescent lamps. One or" the principal difficulties has been in reducing the noise level of the dimming control system. Due to the use of relatively complicated unitary core structures in the past employing narrow legs in the magnetic circuit and due to the combinations of windings on the same core structure the high noise level has not been successfully reduced. The noise characteristic is a very signicant factor in many applications of dimming control systems. High noise levels are particularly objectionable in applications such as auditorium, stage, residential and funeral parlor illumination.

Furthermore, the use of narrow legs in the core structure imparted an inherent structural weakness in the core structure. As a consequence, such core structures of the prior art required special reinforcing members to prevent breakage or' the core structures. Also, they unitary core structures of the prior art necessarily required cases of relatively large transverse cross-sectional area. In many appiications the dimming apparatus is concealed within the iixture where there is no limitation along the longitudinal dimension since lamps are elongated. However, the limitations of the transverse dimensions of the case used to house the dimming control system may in some fixture designs be a critical factor. Further, most of the fluorescent lamp dimming circuits and apparatus which heretofore have been available have not provided a generally satisfactory terminal open circuit voltages across the lamp for a wide range ot dimming control settings.

The dimming control, as the term is used herein, is a device, such as a variable transformer, which is used to vary the input voltage supplied to the lamp terminals and is usually at some remote location from the lighting ixture. The dimming control is used in conjunction with a dimming control system, which as a matter of commercial practice is housed in a separate case and located near the `lighting iixture. A change in the dimming control setting resulls in a change in the input voltage across the terminals of the lamp. The purpose of the dimming control system is to operate the lamp at a selected level of luminous intensity as determined by the dimming control.

lt is desirable that the lamps start over a wide range of dimming control settings. Thus, if the dimming control is set at a low level of luminous intensity, the dimming circuit should ignite the lamp and reliably maintain the lamp at the selected level of luminous intensity without appreciable variations in luminous intensity or without requiring a shift in the control setting to a higher level of luminous intensity and then a second shift back to the desired level.

Accordingly, a general object of the invention is to provide a new and improved circuit and apparatus for adjusting the luminous output of electric discharge lamps.

A more specic object of the invention is to provide a dimming control system having improved noise characteristics which will operate a rapid start iluoresceut lamp at selected levels of luminous intensity.

Another object of the invention is to provide a dimming control system for one or more rapid start uorescent lamps which will start the lamps reliably at a Wide range of settings ofthe dimming control.

Another object of the invention is to provide a dimming control system in which the power factor capacitor, the core structures and coils in the system can be so arranged along a longitudinal axis of a case so that the transverse dimensions of thel case are at a minimum to permit the case to be eectively concealed in a lighting lixture.

A further object of the invention is to provide a dimming control system that can be economically manuacturcd from commercially available components.

Still another object is to provide core structures for the electromagnetic circuits that are structurally sound.

In accordance with the invention, the dimming control system includes a novel arrangement of a magnetically isolated linear reactor and a nonlinear transformer which superimposes a voltage spike on the peak of the approximately sinusoidal open circuit input voltage at the lamp terminals which tires the lamps at each half cycle during a low brightness condition of the circuit. The dimming control system also includes a separate high leakage reactance ballast transformer which functions as a current limiting impedance and provides an additive voltage that combines with the superimposed voltage spike to lire the lamp at each half cycle.

in another aspect of the invention the superimposed voltage spike increases as the sinusoidal input voltage across the lamp terminals decreases so as to provide as substantially constant peak voltage to lire the lamp over a wide range of settings of the dimming control.

Another aspect of the invention involves an electromagnetic peaking circuit which is comprised of linear reactor and a nonlinear transformer having a limited number of inverted U-shaped laminations which was found to be particularly suitable for the dimming control system disclosed herein.

A nonlinear transformer, as the term is used herein, is an inductive device and includes such devices as saturabie reactors, transformers, autotransformers having saturating characteristics which for practical purposes are effective in the circuit only during the period their cores saturate and desaturate. A voltage spike, as the term is used herein, is defined as a sharp voltage increment, or impulse in contradistinction to the peak voltage, which is the maximum net open circuit voltage across the lamp and includes the voltage spike when the spike is superimposed on the lamp circuit.

The subject matter of the invention is set forth in the appended clai'ns. The invention itself, however, together with further objects and advantages thereof may be understood by referring to the following description taken in connection with the accompanying drawings in which- FIG. l is a schematic circuit diagram of the dimming control system of one embodiment of the invention;

FIG. 2 is a diagram showing the lamp terminal open circuit voltage for half a cycle for a dimming control setting of bright and dim on the dimming control in the circuit shown in FIG. 1;

FIG. 3 illustrates a schematic diagram of a dimmingV control system of another embodiment of the invention;

FIG. 4 is a diagram showing the lamp terminal open circuit voltage for a half cycle for settings of brigh and dim on the dimming control in the circuit shown in FIG. 3;

FIG. y5 is a diagrammatic illustration of the coreI and winding arrangement of the peaking circuit of the invention; and

FIG. 6 is a plan view of the dimming control system case with the cover removed to show the longitudinal arrangement of the component parts of the system.

The rectangle formed by the dashed lines of FIGS. 1 and 3 encloses the dimming control system of the invention. Referring to FIG. 1 and FIG. 3, the illustrated dimming control system starts and maintains the luminous intensity of an electric discharge lamp 10, which is shown as a uorescent lamp. In the illustrated circuit the lamp 10 may be a 40-watt rapid start uorescent lamp which comprises an elongated tubular cylindrical envelope 11 having sealed into the ends thereof the lamentary cathodes 12 and 13, which are illustrated in the form of a coil of tungsten wire. The larnents 12, 13 are activated with oxides of alkaline earth metals, such as mixtures of barium and strontium oxides. The envelope is filled with a starting gas, such as argon, at a Vpressure of a few millimeters and a small quantity of mercury. The interior of the envelope 11 is coated with a phosphor which converts the 'ultraviolet radiation produced by the discharge into visible light. The outside surface of the envelope 11 is coated with a water-repellent substance which makes it possible to start the lamp 10 under normal atmospheric conditions and low voltages Vwhen the lamp 10 is positioned close to a conducting means and a suitable potential difference is provided with respect to one of the cathodes 12, 13. The conducting plate 14 located in proximity to the lamp envelope 11 serves as such a conducting means and is connected to ground. In a commercial fixture the metal reflector of the grounded fixture may perform the function of the conductive plate 14. The normal spacing of the plate 14 is approximately three-eights (S/s) of an inch from the envelope 11.

The reference character 15V designates generally the ballast Vautotransformer which includes a primary 16, a high leakage reactance secondary 17, a second secondary 18, and the two cathode heating windings 19 and 20.

As shown in FIG. 6, the magnetic core 21 of the ballast autotransformer 15 is comprised of a laminated central winding leg 22 and the E-shaped laminations 23 which -abut the sides of the winding leg 22. 'The middle legs of the E-shaped laminations 23 form magnetic shunts 24, 25, the ends of which are spaced from the central winding leg 22 by an air gap 27. v

The coil structure 28 includes the primary winding 16, the cathode heating windings 19, 20, and the second secondary V18. These windings are disposed about the central winding lleg 22 in window 29. The secondary high leakage reactance winding 17 of the autotransformer 15 is disposed about central winding leg 22 in window 30.

Referring again to FIGS. 1 and 2, the cathode heating windings 19, are tightly coupled with the primary 16 in order that the supply of cathode heating current` is maintained at a constant value'. The loose coupling between the pri-nary 16 and secondary winding 17 is required in order to obtain the high leakage reactance which is necessary to limit the current flowing through the lamp 10 which has a negative resistance characteristic.

The second secondary winding 18 is connected in series with the power factor capacitor 31 across the power supply by terminal connections 32, 33. The purpose of the second secondary winding 13 is to increase thervoltage across the capacitor 31 above the source voltage, thereby reducing the size of the capacitor required to correct the overall power factor of the circuit. The capacitor 31 draws a leading current from the primary 16 which offsets the lagging magnetizing current.

It should be readily apparent that by theV elimination of the capacitor 31 and the second secondary winding 18 that the circuit can be readily converted to Va low power factor ballast arrangement. As will be hereinafter more fully described, such a ballast arrangement may bey used with each lamp when more than'one lamp is to be operated by a single peaking circuit'in accordance with the invention.

The cathode heating windings 19, 20 are connected across the cathodes 12, 13 by meansY of conductors 34, 35 and 36, 37 respectively. The cathode heating winding 2t) is shown in an autotransforrner relationship with the primary 16, while the other cathode heating winding 19 is shown in an isolated secondary'relationship with the primary 19. It should be evident that a circuit designer Yhas a considerable amount of exibility in locating the cathode heating windings, providing the windings Iwill supply a constant heating current to the cathodes, 12, 13.

T he pri-mary winding 16 is connected across a normal 120 volt, 60 cycle commercial power supply which is connected with the circuit at the terminals, 38, 39, the terminal 38 being the high side and the terminal 39 being the'low side of the supply. The low side is arranged so that it is at the same voltage potential as inductive plate 14 and is grounded as indicated by a dotted ground connection 4t). Y

Referring now specifically to FIG. 3, one end of the high leakage reactance secondary 17 is connected by means of a conductor 42 to a secondary Winding 43 of a nonlinear transformer 44, which also has a primary winding 45. The primary and secondary windings of the nonlinear transformer 44, as shown in FIG. 3, are in Vautotransformer relationship. A tap 46 of the nonlinear transformer 44 is connected with one end of a linear reactor 47, while the other end of the linear reactor 47 is connected to the high voltage side of the power supply at connection 48.

The primary winding 45 of the nonlinear transformer 44 is connected to a slider or adjustable tap 49 of a variable autotransformer or dimming control 50 connected across the power supply, which serves as a dimming control. In the practice of the invention a step# down or a step-up variable autotransformer may be used as required. In one commercial exemplification of the Vinvention a variable autotransformer having a range from 0 to 130Vvolts alternating current was employed. In such an arrangement a slight step-up inV voltage is obtained when 11S-120 volt power supply is used.V

The peaking circuit includes the linear reactor 47 and the nonlinear transformer 44, the'primary 45 and the secondary 43 as shown in FIG. 3, being connected in autotransformer relationship. This permits the dimming control system to make maximum use of the voltage of the device.

In a diming control system operating a l0-watt rapid start lamp it is desirable that an open circuit peaking voltage of approximately 325 `volts be maintained at the lamp terminals over the widest range of dimming control settings. An advantage of the peaking circuit shown in FIG. 3 is that the voltage spike supplied by the secondary 43 of the nonlinear transformer 44 will increase as the setting of the dimming control is adjusted to dethe variable autotransformer is moved toward the position D of maximum dimness, the voltage across the primary winding 4S and linear reactor i7 increases with the result that the voltage spike superimposed on the sinusoidal input voltage across the lamp increases. Since the open circuit voltage across the lamp for a given setting of the slider 49 of the dimming control 5t) is equal to the sum of the voltage spike, the line voltage, and the secondary voltage of the ballast transformer 1S, the net elfect is that an approximately constant open circuit peak voitage is maintained across the lamp i@ for restarting of the lamp it) at each half cycle.

illustrated in FIG. 5 in more detail is the arrangement of the core structures and windings of the peaking circuit. A winding Si Wound around a magnetic core 52 comprises the linear reactor 45'?. The primary winding i5 and the secondary winding 43 wound around a magnetic core 53 comprise the nonlinear transformer 44. The primary winding '55 and the secondary winding 43 are in autotransormer relationship with each other. Gne end of the winding 51 of the linear reactor 47 is connected by means of conductor S4 to the tap 45. The other end is at the terminal d which is for connecting to the high side of the power supply. A first terminal Se oi the secondary winding t3 provides a means for connecting to the high leakage reactance secondary i7 and a second terminal 55 provides a means for connecting to the slider 4% of the dimming control Si). The core 53 is built of a suicient number of iaminations to provide a relatively small cross sectional area that makes the core readily saturable. in the illustrated exemplification of the invention, eight U-shaped laminations are used, adjacent laminations being reversed to break the joints and being constructed of thin sections of grain oriented electrical steel.

The linear reactor 47 is built up of two adjacent stacks of E-shaped laminations 57 with the ends of their legs in an abutting relationship. The winding Si is disposed around a middle leg 5S.

rEhe Way in which a voltage spike is superimposed on the open circuit voltage across the lamp terminals will now be described. lThe total flux in the peaking circuit is distributed between the core S2. of the linear reactor s? and core 53 of nonlinear transformer 4d. The variation of total flux is substantiaily sinusoidal and cycles at the frequency of the pover supply. At the beginning of a cycle saturation occurs very quickly in the legs of the core 53 of the nonlinear transformer 44E. The ux in the linear reactor d?, however, increases slowly until the flux in the nonlinear transformer 44 passes the point of saturation at which time the ux in the nonlinear reactor i7 undergoes a rapid increase. Since the iiux in the core 53 of the nonlinear transformer 44 undergoes a very rapid change at the'heginning of each half cycle, a voltage spike is generated in its secondary winding d3. Since this voltage spike occurs approximately at the same time that the input lamp voltage from the dimming control di? and ballast secondary li' is at its maximum value and since the spike generated and the input lamp voltage are of the same polarity, the spike is superimposed on the sinusoidal input lamp voltage.

In view of the fact that the voltage across the primary winding l5 of the nonlinear transformer 44 increases as the slider 49 of the dimming control is moved away from a position of maximum brightness B, the spike generated in the secondary 43 will increase to maintain a fairly constant open circuit peak voltage at the lamp lil. Thus, in accordance with the invention it is possible for the dim ming control system to reliably operate the lamp l@ at a wide range of luminous intensity levels.

ln FiG. 1 another embodiment of the invention is illustrated in which the linear reactor 59 and the primary i5 of the nonlinear transformer 6i) are connected in series across the alternating voltage supply. In such an arrangement a very narrow spike is generated across the nonlinear transformer Gti. The spike in the primary el produces a corresponding spike in a separate secondary Winding 62 and in this manner is superimposed upon the voltage across the lamp it).

Referring now to FIGS. 2 and 4, it can be seen that for a setting of the dimming control near the maximum dim position D', a comparatively low root mean square voltage appears at the lamp to. However, the peak voltage resulting from the spike being superimposed upon the sinusoidal input Voltage is sucient to re the lamp. In this manner the lamp lltl operates at a low brightness level and retires at each half cycle. When the slider 49 of dimming control Sil is adjusted toward the position of maximum brightness B, the root mean square voltage across the lamp l0 is considerably greater causing the lamp iii to operate at a higher level of brightness and also causing the conducting period of the lamp l@ to increase. It will be noted that in the apparatus of FIG. 3 when the slider 49 of dimmer control 50 is set at B, a substantially sinusoidal voltage Without any appreciable peaking effect appears across the lamp lit as shown in FIG. 4.

ln PEG. 6 the arrangement of the principal components in the dimming control system case 41 is shown. The power factor correcting capacitor 31 is located at one end of the case il and is separated from the ballast transformer 15 by an insulator 63. As hereinbefore described, the core structure 2l is formed by the E-shaped laminations batting against the laminations of the central leg 22. The coil structures 28 and 17 may be held against the central leg 22 by wedges (not shown).

In an adjacent portion of the case di and separated from the ballast transformer 15 by an insulator 65 is the nonlinear transformer 442. rl'he coil structure 66, which includes the primary winding 45 and secondary winding i3 is disposed around a leg d'7 ot the core structure 53 formed by alternately inverted U-shaped laminations.

The linear reactor 47 is located in the lower end of the case il and is separated from the nonlinear transformer i4 by an insulator 69. All of the components are embedded in a suitable potting compound such as asphalt.

It is to be noted that none of the laminations employ any unusual congurations or have any narrow legs or bridged sections. The laminations of the ballast transformer i5 are of the type commercially used for rapid start ballast circuits. The core structures 52, 53, 2l of the dimming control system are separate units. Thus, the system of this invention provides for the magnetic isolation, so far as is practically feasible, of all the peaking and ballast elements of the system. It was found that such an arrangement results in an appreciable reduction in noise as compared to other dimming control systems of the electromagnetic type. Accordingly, the dimming control system of this invention is particularly suitable for many applications, such as, stage, auditorium, residential and funeral parlor lighting purposes where a high noise level is objectionable.

Further, two additional advantages are realized by the arrangement in accord with the inventions. One is that the dimming control system can utilize commercially available core laminations and coils. Secondly, the transverse dimensions of the components of the dimming control system and the case il are signicantly reduced over comparable components used in the prior art. The transverse dimensions are important in a fixture design in which it is necessary to conceal the case of the dimming control system Within the lamp iixture.

The operation of the dimming control system of FIG. 3 will now be described in more detail. When the slider i9 of the dimming control Sti* is at position B, the open circuit voltage across the primary and secondary voltages of the ballast transformer 15 are suicient to lire the uorescent lamp lil. Once the lamp itl ignites, the high leakage reactance of the secondary winding i7 of the ballast transformer provides the necessary ballasting action required because of the negative resistance characteristic of the lamp 10. The cathode heating windings 19, are closely coupled to the primary winding 16 of the ballast transformer 15 and provide the filaments 12,V 13 respectively with a substantially constant current for heating the cathodes of the lamp 10.

It is to be noted lthat when the slider 49 is in the position B, no Voltage appears across the primary 45 of the nonlinearV transformer 44 and the reactor 47 and no voltage spike is introduced by the secondary 43 into the lamp circuit. In effect, the primary 45 and the reactor 47 are by-passed and the lamp 10 operates in the normal manner.

As the slider 49 is moved away from the position of maximum brightness B, a progressively increasing Voltage is being applied to the primary 45 of the nonlinearV transformer 44 and the linear reactor 47. Also, as the slider 49 is moved in this direction, the sinusoidal input voltage `to the lamp 10 and the current being supplied to the lamp 10 correspondingly diminish. With a diminishing current supply to the lamp 10, the energy emitted at the cathodes decreases and the uorescent coating of the lamp receives a reduced amount of radiation with the result that the luminous intensity of the lamp declines.

Unless some means is provided in the dimming control system for firing the lamp 10, it would normally stop discharging when the input voltage reaches a certain level. The peaking circuit provides the necessary voltage spike at each half cycle to reire the lamp. Since the voltage spike occurs at thefrequency of 60 cycles per second, the operation of the lamp 10 is in effect continuous.

It is to be noted that as a decreasing input voltage appears across the lamp 10 to cause dimming, an increasing voltage isV being applied across the primary 45 of the nonlinear transformer 44 and the linear reactor 47 to proportionately step up the voltage spike. Such an arrangement provides a substantially constant open circuit peak voltage for a wide range of the dimming control settings, and results in stable lamp operation at the selected levels of luminous intensity. v Y vrom the foregoing description Vit should be apparent that a single peaking circuit of the invention and the dimming control can be used with a plurality of lamps and ballasts as Well as a single lamp and ballast. In the embodiment shown in FIGS. l and 3, a second secondary 18 is used in conjunction with the power factor correcting capacitor 31 for the purpose of reducing the size of the capacitor. Asis wellV known in the'art, the power factor canY be corrected by other methods without coupling the winding 18 with the' ballast transformer 15. For example, such an arrangement would not normally be used if the peaking .circuit were to oper-ate more than one lamp. Modified in this manner, a plurality of ballast transformers and lamps can be operated from one peaking circuit and dimming control by connecting the three leadsV of each ballast `transformer as modified with the corresponding three leads of the peaking circuit.

- While several particular embodiments of the invention Y have been described above, many modifications may be made. It is to berunderstood, therefore, that it is intended by the appended claims to cover all such modifications as fall within the -true spiritand ,scope of the invention.

What is claimed as newV and desired to be secured by Letters `Patent of the United States is: Y 1. A dimming control system for operating a hot cathode fluorescent lamp at various brightness levels from an lalternating power supply including a low and a high side, said system comprising first and second input leads connected to said low and high side respectively, a high leakage reactance transformerV having a primary connected across said input leads and a high leakage reactance secondary, a linear reactor, a fluorescent lamp, av nonlinearV transformer having a primary and a secondary, a pair of transformer output leads, one of said output leads connecting one end of said high leakage reactance secondary with one end of said lamp and the other of said output leads connecting said primary to the other end of said lamp, said linear reactor and said primary of the nonlinear transformer being connected in series across said input leads, and circuit means connecting said secondary of the nonlinear transformer, said high leakage Vreactance secondary and said lamp in series circuit relationship across said adjustable tap and said first input lead.

2. peaking circuit for superimpo-sing a voltage spike on an input voltage supplied to a hot cathode fluorescent lamp from an alternating current source and regulated by a dimming control having an adjustable tap, said lamp being connected across a ballast transformer having a primary and a high leakage reactance secondary, said peaking circuit comprising a nonlinear transformer having a core structure formed of alternately inverted U- shaped laminations including a primary and a secondary winding disposed on said core structure in autotransformer relationship and a tap between saidV primary and secondary windings, said nonlinear transformer having a first terminal for connecting said secondary winding in series circuit lrelationship with said high leakage reactance secondary and a second terminal for connecting said primary winding to said adjustable tap, lsaid nonlinear ltransformer being magnetically isolated from said ballast transformer; and a linear reactor connected at one end to said tap of the nonlinear transformer and at the other end having a terminal for connecting to said alternating current source.

3. A peaking circuit for superimposing a voltage spike on a voltage'supplie'd to a hot cathode fluorescent lamp from an alternating current source and controlled by a dimming control having an adjustable tap, said hot cathode fluorescent lamp being connected in circuit with a ballast transformer having a primary and a high leakage reactance secondary, said primary. being connected across a pair of input leads, said peaking circuit comprising a linear reactor, a nonlinear reactor for producing a voltage spike and having a primary and a secondary, said primary of said nonlinear reactor and said linear reactor being connected in series for energization from said input leads, lsaid nonlinear reactor having a pair of terminals for applying the voltage spike to said lamp, one of said terminals being adapted for connection to the adjustable tap of the dimming control and the other of said terminals being connected to the high leakage reactance secondary of the ballast transformer, the connections between said latter' terminal and said high leakage reactance secondary placing saidvsecondary of said nonlinear reactor and said high leakage reactance secondary in series circuit relationship.

4. In an apparatus for operating a hot cathode fluorescent lamp at various brightness levels, said apparatus including a dimming control connected across an alternating current supply and having an adjustable tap,V a ballast transformer with a primary and a high leakage reactance secondary and a pair of input leads for connection in circuit with the alternating current supply, and a circuit meansincluding output leads for applying the output of the ballast transformer to the lamp, the improvement comprising a peaking means including a linear reactor and a nonlinear transformer having a primary and a secondary, circuit means connecting said primary of the nonlinear transformer and said linear reactor in series circuit across the input leads and circuit means including a rst terminal for connecting one end of the secondary of the nonlinear `transformer to the adjustable tap of the dimmingV control and a second terminal connecting the other endV of the secondary of the nonlinear transformer in series relationship with the high leakage reactance secondary of the ballast transformer.

5. A peaking circuit for superimposing a voltage spike on an input voltage supplied to a hot cathode uorescent lamp from an alternating current source and regulated by a dimming control having an adjustable tap, said lamp being connected across a bailast transformer having a primary and a high leakage reactance secondary, said peaking circuit comprising a noniinear autotransformer including a primary, a secondary and a tap, said nonlinear autotransformer having a first terminal for connecting said secondary of said nonlinear autotransformer in series circuit relationship with said high leakage reactance secondary and a second terminal for connecting said nonlinear autotransformer to said adjustable tap, said nonlinear autotransformer being magnetically isolated from said ballast transformer; and a linear reactor connected at one end to said tap of the nonlinear autotransformer and having a terminal at the other end for connecting said linear reactor to said alternating current source.

6. A peaking circuit for superimposing a voltage spike on an input voltage supplied to a hot cathode tiuorescent lamp from a power source and regulated by a dimming control having an adjustable tap, said lamp `being connected across a ballast transformer having a primary and a high leakage reactance secondary, said peaking circuit comprising a nonlinear transformer including a primary and a secondary, said nonlinear transformer having a first terminal for connecting said secondary of the nonlinear transformer in series circuit relationship With said adjustable tap and a second terminal connecting said high leakage reastance secondary, and a linear reactor connected in series with said primary of the nonlinear transformer, said serially connected linear reactor and primary of the nonlinear transformer having a pair of terminals for connecting said serially connected linear reactor and primary across said power source.

7. A dimming control system for operating a hot cathode uorescent lamp at various brightness levels from an alternating power supply including a low and a high side, said system comprising a rst .and second input lead for connection to said low and high side of the power supply respectively, a high leakage reactance transformer having a primary connected across said input leads and a high leakage reactance secondary, a linear reactor, a fluorescent lamp, a pair of transformer output leads, one of said output leads connecting said lamp with one end of said high leakage reactance secondary and the other of said output leads connecting one end of said primary with said lamp, a nonlinear transformer having a primary and a secondary, a variable autotransformer connected across said input leads and having an adjustable tap, said linear reactor and said primary of the nonlinear transformer bein" connected in series across said adjustable tap and said second input lead, and circuit means. connecting said secondary of the nonlinear transformer and said high leakage react'ance secondry in series circuit relationship.

8. Apparatus for operating a hot cathode fluorescent lamp at various brightness levels regulated by a dimming control energized by an alternating voltage supply including a high side and a low side and having an adjustable tap, said apparatus comprising lirst and second input leads for connection with the high side and low side respectively of the alternating voltage supply, a ballast means having a primary connected across said input leads and a high leakage reactance secondary, a peaking means including a linear reactor and a nonlinear transformer having a primary and a secondary, a pair of output leads, one of said leads being adapted for connecting one end of said high leakage reactance secondary to one end of the fluorescent lamp and the other of said output leads lbeing adapted for connecting one end of the primary to the other end of the uorescent lamp, circuit means connecting said primary of said nonlinear transformer and said linear reactor in series circuit relationship, said serially connected primary and linear reactor having a lirst and second terminal, said rst terminal being connected to said r'irst input lead and said second terminal being adapted for connection to the adjustable tap of the dimming control, said iirst terminal connecting said secondary of the nonlinear transformer in series circuit relationship with high leakage reactance secondary, said secondary of the nonlinear transformer being connected in autotransforrner relationship with the primary of the nonlinear transformer.

9. Apparatus for operating a hot cathode fluorescent lamp at various brightness levels from an alternating current supply including a low and a high side comprising first and second input leads for connection to the high side and low side respectively of said power supply, an autotransformer connected across said input leads and having an adjustable tap, a ballast autotransformer having a primary connected across said input leads and a high leakage reactance secondary; a line-ar reactor; a pai-r of output leads for connection across said fluorescent lamp, one of said leads being adapted for connecting one end of said high leakage reactance secondary winding with one end of said lamp and the other of said output leads being adapted for connecting one end of said primary winding of said ballast transformer with the other end of said lamp; a nonlinear transformer having a primary, a secondary in autotransformer relationship with said primary and a tap between said primary and secondary; circuit means connecting said secondary of the nonlinear transformer and said high leakage reactance secondary in series circuit relationship; and circuit means connecting said primary of the nonlinear transformer and said linear reactor in series circuit relationship between said adjustable tap and said first input lead.

lil Apparatus for operating a hot cathode fluorescent lamp at various brightness levels from an alternating current supply including a low and a high side, said apparatus comprising a first and second input lead connected to said high and low side respectively of said power supply, an autotransformer connected across said input leads and having an adjustable tap, a ballast autotransformer 'having a primary connected cross said input leads and a high leakage reactance secondary, linear reactor, a pair of output leads for connection across said lamp, one of said leads being adapted for connecting one end of said high leakage reactance secondary winding with one end of said lamp and the other of said output leads being adapted for connecting one end of said primary winding of said ballast transformer with the other end of said lamp, a nonlinear transformer having a primary and a secondary winding in isolated secondary relationship with said primary circuit means connecting said adjustable tap, said secondary of the nonlinear transformer and said high leakage reactance secondary in series circuit relationship, said linear reactor and said primary of the nonlinear transformer being connected across said input leads.

11. Apparatus for operating a hot cathode fluorescent lamp at various brightness levels regulated by a dimming control energized by an alternating current supply and having an adjustable tap, said apparatus comprising a ballast means having a pair of current limiting terminals for connection across said lamp, a peaking means` including a linear and nonlinear inductive device connected in series for producing a voltage spike, said voltage spike being variable in magnitude as the dimming control is varied, circuit means for applying a voltage across said serially connected linear and nonlinear inductive device, said nonlinear device having a pair of output terminals for applying said voltage spike to said lamp, and one of said output terminals being adapted for connection to said adjustable tap, and the other of said output leads connecting said nonlinear device in circuit with said ballast means.

i2 Apparatus for use with a variable voltage device connected across a source of A.C. power for igniting and operating a gaseous discharge lamp with variations in .intensity of light caused by adjustment of the variable voltage device to provide different voltages, and the volt age device including a brush movable to different tapped positions, the said apparatus comprising: a high leakage reactance transformer including at least a primary Winding and a secondary Winding and means for connecting the primary Winding across the said source, one side of the primary winding having means for connecting the winding to one terminal of said gaseous discharge lamp,` means for connecting one side of the secondary Winding to a second terminal of the lamp, a connection to a second side of the secondary winding adapted to extend to the brush of the variable Voltage device whereby when the primary and secondary windings are connected across the lamp, and the primary winding is connected across the line, and the second side of the secondary winding is connected to said brush, the primary and secondary Vwindings will be connected in autotransformer relation across the lamp but with the resulting voltage determined i2 by the position of said brush, a peaking circuit in the connection of the second side of said secondary for superimposing a peak upon the R.M.S. voltage generated bysaid transformer to aid in starting the lamp, and having means for varying the amplitude of the peak inversely as the R.M.S. voltage produced due to changes of the position of the brush. r

References Cited by the Examiner UNITED STATES PATENTS 12/58 Davis 315-278 X GEGRGE N. WESTBY, Primary Examiner.

ARTHUR GAUSS, RALPH G. NILSOVN, BENNETTV G. MILLER,4 Examiners. 

1. A DIMMING CONTROL SYSTEM FOR OPERATING A HOT CATHODE FLUORESCENT LAMP AT VARIOS BRIGHTNESS LEVELS FROM AN ALTERNATING POWER SUPPLY INCLUDING A LOW AND A HIGH SIDE, SAID SYSTEM COMPRISING FIRST AND SECOND INPUT LEADS CONNECTED TO SAID LOW AND HIGH SIDE RESPECTIVELY, A HIGH LEAKAGE REACTANCE TRANSFORMER HAVING A PRIMARY CONNECTED ACROSS SAID INPUT LEADS AND A HIGH LEAKAGE REACTANCE SECONDARY, A LINEAR REACTOR, A FLUORESCENT LAMP, A NONLINEAR TRANSFORMER HAVING A PRIMARY AND A SECONDARY, A PAIR OF TRANSFORMER OUTPUT LEADS, ONE OF SAID OUTPUT LEADS CONNECTING ONE END OF SAID HIGH LEAKAGE REACTANCE SECONDARY WITH ONE END OF SAID LAMP AND THE OTHER OF SAID OUTPUT LEADS CONNECTING SAID PRIMARY TO THE OTHER END OF SAID LAMP, SAID LINEAR REACTOR AND SAID PRIMARY OF THE NONLINEAR TRANSFORMER BEING CONNECTED IN SERIES ACROSS SAID INPUT LEADS, AND CIRCUIT MEANS CONNECTING SAID SECONDARY OF THE NONLINEAR TRANSFORMER, SAID HIGH LEAKAGE REACTANCE SECONDARY AND SAID LAMP IN SERIES CIRCUIT RELATIONSHIP ACROSS SAID ADJUSTABLE TAP AND SAID FIRST INPUT LEAD. 